Harmonising notes outside of a scale?

Just started learning some concepts of harmonisation. I have learnt that you can harmonise in 3rds, 5ths etc by goig up that ammount in the swcale and using that note as a harmoniser. However, what if you have a note that's outside the typical scale, like a flatted note in a blues scale, or just a note put in there for its own musical sake? how do you harmonise these?Any insight would be appreciated, thanks

Notes out side of the scale are generally going to be Non chord tones meaning that they wont belong to the chord underneath them at all. So either hold the chord before it, or start the next chord early and have the non chord tone resolve to be part of the chord. You can do the same things with notes that are part of the scale but don't belong to the chord under them. It adds variety and interest to the music not having the chords exactly follow the melody notes.

If you really want to harmonize them you can use chords borrowed from other scales. Say you are writing in c major you can borrow from c minor, c harmonic minor, etc. or as suggested if you like the way it sounds go for it.

no insight involved. for non-diatonic harmony, the only real and practical approach is to rely on your ear.

sadly, yes. The only thing you can really do is see if the non-diatonic implies a certain chord, or you can you use the harmony note to create an interval that implies a chord that would transition well into the next one. Try to keep the music stable, and make sure the harmonization isn't interfering with the overall movement.

no insight involved. for non-diatonic harmony, the only real and practical approach is to rely on your ear.

I beg to differ.

Say you come across a b7 in a major key. Well, you know how to harmonize the natural 7 (the third is minor and the fifth is diminished, if you're using thirds), so you can keep the third and fifth the same, just moving the melody note down to the b7, and you have a major third and a perfect fifth.

What if you come across a b3? Well you know the parallel minor key builds a major chord on the third degree, so a major third would work. A perfect fifth can work too, it'll just have to alter the natural 7th.

So you see that there's a rather simple method for coming up with harmonies. I realize I only dealt with thirds and fifths, but the same deal can apply to any other harmonic interval.

Now this doesn't really account for chromatic passing tones (like the one in the blues scale), but there are ways around that. Say you have a line (in C major) that goes C E F Bb B C. If you wanted to go straight thirds, you could do E G A D D# E, but I would like to avoid those parallel thirds. How about we harmonize the Bb with an F. That gives us E G A F D# E. This is kind of cool, because it doesn't just use that B major third dyad as a passing tone thing, it uses it as a sort of functional dominant (7 and #9).

Only play what you hear. If you don’t hear anything, don’t play anything.-Chick Corea

Say you come across a b7 in a major key. Well, you know how to harmonize the natural 7 (the third is minor and the fifth is diminished, if you're using thirds), so you can keep the third and fifth the same, just moving the melody note down to the b7, and you have a major third and a perfect fifth.

What if you come across a b3? Well you know the parallel minor key builds a major chord on the third degree, so a major third would work. A perfect fifth can work too, it'll just have to alter the natural 7th.

So you see that there's a rather simple method for coming up with harmonies. I realize I only dealt with thirds and fifths, but the same deal can apply to any other harmonic interval.

Now this doesn't really account for chromatic passing tones (like the one in the blues scale), but there are ways around that. Say you have a line (in C major) that goes C E F Bb B C. If you wanted to go straight thirds, you could do E G A D D# E, but I would like to avoid those parallel thirds. How about we harmonize the Bb with an F. That gives us E G A F D# E. This is kind of cool, because it doesn't just use that B major third dyad as a passing tone thing, it uses it as a sort of functional dominant (7 and #9).

you're talking about borrowing chords. totally different. your deal with the bVII is just a matter of borrowing a chord from the parallel minor.

the way i understand it, he's talking about harmonizing a note not in the scale. for example, how would one harmonize a Db within a melody in the key of C? how would one harmonize an F# within a melody in the key of C? it all depends on the ear (unless you know you're trying to imply a certain chord).

^^^Maybe so but it may not be evident without more underlying support. It comes down to sound.... nothing else. Book answers suck and are impractical. Theory on paper needs only a match and fuel source. You still have to use your ears.